Clathrate hydrates are ice like substances that can store guest gases, typically CO2, CH4, and other small molecules. Reported clathrate hydrates store guest molecules in cages of hydrogen-bonded water molecules exist in cubic forms, and a tetragonal form. Clathrates are disclosed as accumulating high concentrations of CO2. Clathrates take up these gases at appropriately low temperatures and gas pressures. Notably, 1 liter of clathrate slurry can contain about 11 liters of guest gas.
Under suitable thermodynamic conditions, gases with molecular diameters between 0.35 nm and 0.75 nm dissolved in water can transform into inclusion compounds where the gas solute molecules occupy sites in aqueous cage structures formed by the hydrogen bonded water molecules. Such inclusion compounds are known as clathrate hydrates. CO2, CH4, N2, SO2, NO, CO, H2, and small (C2 and C3) hydrocarbons are among the gas phase species that can form stable clathrate hydrates. The formation of clathrates hydrates is often carried out close to ambient gas pressure facilitated by clathrate-promoter molecules, e.g., tetra hydro furan (THF), sodium dodecyl sulfate (SDS) propylene oxide, 1,4-dioxane, acetone, 1,1-dimethylcyclohexane, methyl tert-butyl ether (MTBE), and methylcyclohexane. Ambient gas pressure shall be understood to mean 1 atm equal to 101325 Pa or 1013.25 millibars or hectopascals. It also is equivalent to 760 mmHg (torr), 29.92 inHg, 14.696 psi. “Close” as applied to ambient pressure shall be understood to mean±about 50%. Cathrates are also produced without clathrate enhancers. Conveniently, such production occurs at pressures of tens of bar up to 150 bar. These promoters are usefully water miscible and thus dissolved in the water. In one embodiment clathrate hydrates are produced by cooling a solution of 10% THF (by weight) in water to approximately 2° C. The solution is exposed to CO2 gas at ambient pressure (1 bar absolute).
The conversions products of the present invention are distinct from steam electrolytic conversions. The instant disclosure covers electrochemistry in the presence of clathrates. Clathrates do not exist at temperatures above about 10-15° C.
Catalysts may be employed in an embodiment of the basic process. However, catalysts are not a necessary for the basic process of employing clathrates in electrochemistry.
Porous electrodes are noted. Reference is made to Sumioka, et al. “Porous electrode substrate and method for producing the same,” U.S. Pat. No. 8,574,758 and to Sato et al. “Porous electroconductive material and process for production thereof; electrode and process for production thereof; fuel cell and process for production thereof; and electronic instrument, mobile machine, electric power generating system, cogeneration system, and electrode reaction-based apparatus,” U.S. Pat. No. 8,419,913. Nanoparticle coated electrodes are also noted. Reference is made to Chen et al, “Electrolytic water treatment device having sintered nanoparticle coated electrode and method for making acid or basic water therewith” U.S. Pat. No. 8,227,643; and Hosokowa et al, Nanoparticle Technology Handbook, Second Edition, Elsevier (2012).
Noted is the use of a flat copper electrode the faradaic efficiencies for higher hydrocarbon production, such as propane.
Clathrates hydrates can exist in aqueous or ammonia systems which are contemplated in the present disclosure. Reference is made to Chapoy, et al., “Low-Pressure Molecular Hydrogen Storage in Semi-clathrate Hydrates of Quaternary Ammonium Compounds,” J. Am. Chem. Soc., 2007, 129 (4), pp 746-747; and Arjmandi, et al. “Equilibrium Data of Hydrogen, Methane, Nitrogen, Carbon Dioxide, and Natural Gas in Semi-Clathrate Hydrates of Tetrabutyl Ammonium Bromide,” J. Chem. Eng. Data, 2007, 52 (6), pp 2153-2158.
Clathrates are usefully produced in a continuous-flow reactor and used in a continuous-flow electrochemical cell. An embodiment is depicted in FIG. 1. There CO2 is captured from a CO2-rich gas stream, such as flue gas, in a scrubber reactor. The CO2-loaded clathrates/water mixture has the consistency of slush. It is pumped into a chemical reactor cell where electrochemical or catalytic conversion of the trapped CO2 gas is carried out. Once the clathrates are depleted of some or all of the CO2, the slush is recycled back into the scrubber. Products produced in the electrochemical or catalytic reactor are continuously removed.
A diagrammatic electrochemical cell is shown in FIG. 2a and a flow cell in FIG. 2b 
All publications cited herein are incorporated by reference in their entirety. Particular reference is made to the following publications, the teachings of which are incorporated herein by reference in their entirety:
1. Clathrate Hydrates of Natural Gases, Third Edition., Ed, Sloan et al., (CRC Press, Boca Raton Fla. (2008);
2. Hydrates: Immense Energy Potential and Environmental Challenges (Green Energy and Technology) by Carlo Giavarini and KeithHester (Springer; 2011);
3. M. M. Halmann, Chemical fixation of carbon dioxide, Methods for recycling CO2 into useful products, CRC Press (1993).
4. Li, H.; Oloman, C., “Development of a continuous reactor for the electro-reduction of carbon dioxide to formate Part 2: Scale-up.” Journal of Applied Electrochemistry 37, (10), 1107-1117 (2007).
5. Li, H.; Oloman, C., Development of a continuous reactor for the electro-reduction of carbon dioxide to formate—Part 1: Process variables,” Journal of Applied Electrochemistry 36, 1105-1115 (2006).
6. Papadimitriou et al., “Gas content of binary clathrate hydrates with promoters,” The Journal of Chemical Physics 131(4):044102 (2009).
7. Sabil, Khalik M., “Phase behaviour, thermodynamics and kinetics of clathrate hydrate systems of carbon dioxide in presence of tetrahydrofuran and electrolytes,” Diss. Ph. D. dissertation, Technische Universiteit Delft, Delft, Holanda, 2009.
8. Herslund, et al. “Thermodynamic Promotion of Carbon Dioxide Clathrate Hydrate Formation by Tetrahydrofuran, Cyclopentane and their mixtures,” International Journal of Greenhouse Gas Control 17 (2013) 397-410.
9. “Ammonia clathrate hydrates as new solid phases for Titan, Enceladus, and other planetary systems,” K. Shin, R. Kumar, K. A. Udachin, S. Alavi and J. A. Ripmeester, Proceedings of the National Academy of Sciences 109 (37), 14785 (2012)
10. Nakano et al., U.S. Pat. No. 7,892,694 “Electrolytic membrane, process for producing the same, membrane electrode assembly, fuel cell and method of operating the same”
11. Chokai, et al., U.S. Pat. No. 7,833,644 “Electrolytic membrane.”